1. Field of the Invention
The present invention relates to a method and an apparatus for judging the compatibility of a working surface, and more specifically, to a method and an apparatus for judging the compatibility of a working surface with an optical mouse.
2. Description of the Prior Art
An optical mouse generates cursor signals corresponding to its movement detected by optical reflection. This optical reflection is well known by the industry, thus only a brief description is given as follows.
Please refer to FIG. 1 showing a bottom view of a conventional optical mouse 10. As shown in FIG. 1, the optical mouse 10 has a bottom surface 12 with a hole 14 on it. Through the hole 14, the optical mouse 10 uses a light emitting diode (LED. Not shown in FIG. 1) to irradiate a working surface of the optical mouse, and scan and capture images of the working surface as well as compare the differences of the images. Whenever the captured image changes, a circuit built in the optical mouse 10 can calculate the displacement data of the optical mouse 10, convert the displacement data into axial displacement signals and then transmit the signals to a computer (not shown) via a cable 16. The cable 16 complies with standards such as COM, PS/2 or USB.
Please refer to FIG. 2 showing an assembly diagram 20 of the optical mouse 10. As shown in FIG. 2, the optical mouse 10 further includes an optical module 30 installed above the hole 14 on the bottom surface 12, a circuit board 40 installed above the optical module 30, an optical discriminating unit 42 installed above the circuit board 40, a LED 44 installed above the circuit board 40, and an optical mask 46 installed above the circuit board 40. The optical discriminating unit 42 is for capturing images of the working surface that the optical mouse 10 has passed by to analyze and judge the displacement of the optical mouse 10. The LED 44 is used as a light source of the optical discriminating unit 42, and the optical mask 46 is to prevent light from the LED 44 from directly entering into the optical discriminating unit 42. The optical module 30 includes a lens 32, a first reflection surface 34 and a second reflection surface 36. The circuit board 40 includes an aperture 48 positioned above the lens 32, and the optical discriminating unit 42 is installed above the aperture 48 of the circuit board 40. The first reflection surface 34 protrudes out of the aperture 48 so that it is located between the LED 44 and the optical discriminating unit 42.
Please refer to FIG. 2 along with FIG. 3 showing a side view 22 simplified from the assembly diagram 20 in FIG. 2. As shown in FIG. 3, the LED 44 is opposite to the first reflection surface 34 and generates a ray 27. In addition, since the shape of the mask 46 is designed to prevent the ray 27 from the LED 44 from directly entering into the optical discriminating unit 42, most of the ray 27 will go toward the first reflection surface 34 and be reflected downwards by the first reflection surface 34 to the second reflection surface 36. After being reflected by the second reflection surface, the ray 27 passes through the hole 14 on the bottom surface 12 and irradiates a working surface 50 of the optical mouse 10. The working surface 50 modulates the characteristics of the ray 27 and reflects the ray 27 to the lens 32 to be a reflected ray 28. The reflected ray 28 will be converged and focused on the optical discriminating unit 42 by the lens 32, and the optical discriminating unit 42 judges the movement of the optical mouse 10 according to the change of the reflected ray 28.
However, if the working surface 50 of the optical mouse 10 is highly transparent or in special color (e.g. a piece of glass or a glossy surface), the ray 27 incident on the working surface 50 cannot be completely reflected to the optical discriminating unit 42, so that the optical discriminating unit 42 cannot receive continuous images of the working surface 50, and the cursor of the optical mouse 10 cannot be in the right place. In this case, the working surface should be replaced to solve the problem, however, the user may not necessarily understand the characteristics of the optical discriminating unit 42 so that he is unable to locate the problem, and may even misunderstand that the problem is due to the optical mouse itself.